1. Field of the Invention
This invention relates to a backlash eliminator which eliminates backlash in a gear train while reducing a loss.
2. Description of the Related Art
When a pair of gears are brought into mesh, they should theoretically make a correct intermeshing motion. Since there is a slight pitch error, thermal expansion, warpage of the tooth, warpage of the shaft, thickness of an oil film, or the like, however, the teeth grate against each other, making the motion impossible, causing vibrations or producing a noise. To make a smooth intermeshing motion, therefore, a predetermined amount of clearance (backlash) is provided between the tooth flanks of the pair of gears.
When a load is intermittently imposed on a gear train having such gears sequentially intermeshing, elastic energy accumulated in the gear train is released whenever the load is reduced to zero. When this elastic energy is great, however, tooth flank separation occurs between the tooth flanks because of the provision of backlash, resulting in incorrect transmission of rotation. In particular, in a machine tool, such as a hobbing machine or a grinding machine, which indexes the position of relative rotation between a workpiece and a cutter with high accuracy, the tooth flank separation in the gear train, if any, leads to a corresponding deviation in the indexed position. This makes it impossible to determine (index) the exact rotational position of a rotating table, and is likely to exert direct influence on the machining accuracy of the workpiece.
Various backlash eliminators, which prevent tooth flank separation even under load imposed on the gear train, have been provided under these situations. Such conventional backlash eliminators are disclosed, for example, in Patent Document 1.    Patent Document 1: JP-A-7-180749